| Country: | TUR |
| Type: | otoyol |
| Route: | 1 |
| Alternate Name: | The First Beltway 1. Çevreyolu |
| Established: | 1973 |
| Direction A: | West |
| Terminus A: | , in Eyüp, Istanbul |
| Direction B: | East |
| Terminus B: | Bağdat Ave. in Kadıköy, Istanbul |
| Length Km: | 24 |
| Regions: | Marmara |
| Provinces: | Istanbul Province |
| Cities: | Istanbul |
| Map: | Karte O1 TR.svg |
| Next Type: | O |
| Next Route: | 2 |
Otoyol 1 (en|Motorway 1), abbreviated as O-1 and locally referred to as The First Beltway (tr| 1. Çevreyolu), is a controlled access highway in Istanbul, Turkey. The O-1 serves as the inner beltway and is one of three intercontinental motorways in the city, the others being the O-2, and O-7, as well as connecting the European and Asian parts of the city via the Bosphorus Bridge.
It starts Osmaniye neighborhood in Bakırköy district on the European part, runs through the city over the Golden Horn and the Bosphorus, and terminates in Söğütlüçeşme neighborhood of Kadıköy district on the Asian part. Otoyol 1 is toll-free, however the Bosporus Bridge is a toll bridge in both directions, having its toll plaza at the Asian side. The O-1 is connected via three feeder highways to The Second Beltway.
